From: Omar Sandoval <osandov@xxxxxx> Subject: proc/kcore: clean up ELF header generation Currently, the ELF file header, program headers, and note segment are allocated all at once, in some icky code dating back to 2.3. Programs tend to read the file header, then the program headers, then the note segment, all separately, so this is a waste of effort. It's cleaner and more efficient to handle the three separately. Link: http://lkml.kernel.org/r/19c92cbad0e11f6103ff3274b2e7a7e51a1eb74b.1531953780.git.osandov@xxxxxx Signed-off-by: Omar Sandoval <osandov@xxxxxx> Cc: Alexey Dobriyan <adobriyan@xxxxxxxxx> Cc: Bhupesh Sharma <bhsharma@xxxxxxxxxx> Cc: Eric Biederman <ebiederm@xxxxxxxxxxxx> Cc: James Morse <james.morse@xxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- fs/proc/kcore.c | 354 ++++++++++++++++++---------------------------- 1 file changed, 143 insertions(+), 211 deletions(-) --- a/fs/proc/kcore.c~proc-kcore-clean-up-elf-header-generation +++ a/fs/proc/kcore.c @@ -49,15 +49,6 @@ static struct proc_dir_entry *proc_root_ #define kc_offset_to_vaddr(o) ((o) + PAGE_OFFSET) #endif -/* An ELF note in memory */ -struct memelfnote -{ - const char *name; - int type; - unsigned int datasz; - void *data; -}; - static LIST_HEAD(kclist_head); static DECLARE_RWSEM(kclist_lock); static int kcore_need_update = 1; @@ -73,7 +64,8 @@ void __init kclist_add(struct kcore_list list_add_tail(&new->list, &kclist_head); } -static size_t get_kcore_size(int *nphdr, size_t *elf_buflen) +static size_t get_kcore_size(int *nphdr, size_t *phdrs_len, size_t *notes_len, + size_t *data_offset) { size_t try, size; struct kcore_list *m; @@ -87,15 +79,15 @@ static size_t get_kcore_size(int *nphdr, size = try; *nphdr = *nphdr + 1; } - *elf_buflen = sizeof(struct elfhdr) + - (*nphdr + 2)*sizeof(struct elf_phdr) + - 3 * ((sizeof(struct elf_note)) + - roundup(sizeof(CORE_STR), 4)) + - roundup(sizeof(struct elf_prstatus), 4) + - roundup(sizeof(struct elf_prpsinfo), 4) + - roundup(arch_task_struct_size, 4); - *elf_buflen = PAGE_ALIGN(*elf_buflen); - return size + *elf_buflen; + + *phdrs_len = *nphdr * sizeof(struct elf_phdr); + *notes_len = (3 * (sizeof(struct elf_note) + ALIGN(sizeof(CORE_STR), 4)) + + ALIGN(sizeof(struct elf_prstatus), 4) + + ALIGN(sizeof(struct elf_prpsinfo), 4) + + ALIGN(arch_task_struct_size, 4)); + *data_offset = PAGE_ALIGN(sizeof(struct elfhdr) + *phdrs_len + + *notes_len); + return *data_offset + size; } #ifdef CONFIG_HIGHMEM @@ -241,7 +233,7 @@ static int kcore_update_ram(void) LIST_HEAD(list); LIST_HEAD(garbage); int nphdr; - size_t size; + size_t phdrs_len, notes_len, data_offset; struct kcore_list *tmp, *pos; int ret = 0; @@ -263,7 +255,8 @@ static int kcore_update_ram(void) } list_splice_tail(&list, &kclist_head); - proc_root_kcore->size = get_kcore_size(&nphdr, &size); + proc_root_kcore->size = get_kcore_size(&nphdr, &phdrs_len, ¬es_len, + &data_offset); out: up_write(&kclist_lock); @@ -274,228 +267,168 @@ out: return ret; } -/*****************************************************************************/ -/* - * determine size of ELF note - */ -static int notesize(struct memelfnote *en) -{ - int sz; - - sz = sizeof(struct elf_note); - sz += roundup((strlen(en->name) + 1), 4); - sz += roundup(en->datasz, 4); - - return sz; -} /* end notesize() */ - -/*****************************************************************************/ -/* - * store a note in the header buffer - */ -static char *storenote(struct memelfnote *men, char *bufp) -{ - struct elf_note en; - -#define DUMP_WRITE(addr,nr) do { memcpy(bufp,addr,nr); bufp += nr; } while(0) - - en.n_namesz = strlen(men->name) + 1; - en.n_descsz = men->datasz; - en.n_type = men->type; - - DUMP_WRITE(&en, sizeof(en)); - DUMP_WRITE(men->name, en.n_namesz); - - /* XXX - cast from long long to long to avoid need for libgcc.a */ - bufp = (char*) roundup((unsigned long)bufp,4); - DUMP_WRITE(men->data, men->datasz); - bufp = (char*) roundup((unsigned long)bufp,4); - -#undef DUMP_WRITE - - return bufp; -} /* end storenote() */ +static void append_kcore_note(char *notes, size_t *i, const char *name, + unsigned int type, const void *desc, + size_t descsz) +{ + struct elf_note *note = (struct elf_note *)¬es[*i]; + + note->n_namesz = strlen(name) + 1; + note->n_descsz = descsz; + note->n_type = type; + *i += sizeof(*note); + memcpy(¬es[*i], name, note->n_namesz); + *i = ALIGN(*i + note->n_namesz, 4); + memcpy(¬es[*i], desc, descsz); + *i = ALIGN(*i + descsz, 4); +} -/* - * store an ELF coredump header in the supplied buffer - * nphdr is the number of elf_phdr to insert - */ -static void elf_kcore_store_hdr(char *bufp, int nphdr, int dataoff) +static ssize_t +read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos) { - struct elf_prstatus prstatus; /* NT_PRSTATUS */ - struct elf_prpsinfo prpsinfo; /* NT_PRPSINFO */ - struct elf_phdr *nhdr, *phdr; - struct elfhdr *elf; - struct memelfnote notes[3]; - off_t offset = 0; + char *buf = file->private_data; + size_t phdrs_offset, notes_offset, data_offset; + size_t phdrs_len, notes_len; struct kcore_list *m; + size_t tsz; + int nphdr; + unsigned long start; + size_t orig_buflen = buflen; + int ret = 0; - /* setup ELF header */ - elf = (struct elfhdr *) bufp; - bufp += sizeof(struct elfhdr); - offset += sizeof(struct elfhdr); - memcpy(elf->e_ident, ELFMAG, SELFMAG); - elf->e_ident[EI_CLASS] = ELF_CLASS; - elf->e_ident[EI_DATA] = ELF_DATA; - elf->e_ident[EI_VERSION]= EV_CURRENT; - elf->e_ident[EI_OSABI] = ELF_OSABI; - memset(elf->e_ident+EI_PAD, 0, EI_NIDENT-EI_PAD); - elf->e_type = ET_CORE; - elf->e_machine = ELF_ARCH; - elf->e_version = EV_CURRENT; - elf->e_entry = 0; - elf->e_phoff = sizeof(struct elfhdr); - elf->e_shoff = 0; - elf->e_flags = ELF_CORE_EFLAGS; - elf->e_ehsize = sizeof(struct elfhdr); - elf->e_phentsize= sizeof(struct elf_phdr); - elf->e_phnum = nphdr; - elf->e_shentsize= 0; - elf->e_shnum = 0; - elf->e_shstrndx = 0; - - /* setup ELF PT_NOTE program header */ - nhdr = (struct elf_phdr *) bufp; - bufp += sizeof(struct elf_phdr); - offset += sizeof(struct elf_phdr); - nhdr->p_type = PT_NOTE; - nhdr->p_offset = 0; - nhdr->p_vaddr = 0; - nhdr->p_paddr = 0; - nhdr->p_filesz = 0; - nhdr->p_memsz = 0; - nhdr->p_flags = 0; - nhdr->p_align = 0; - - /* setup ELF PT_LOAD program header for every area */ - list_for_each_entry(m, &kclist_head, list) { - phdr = (struct elf_phdr *) bufp; - bufp += sizeof(struct elf_phdr); - offset += sizeof(struct elf_phdr); - - phdr->p_type = PT_LOAD; - phdr->p_flags = PF_R|PF_W|PF_X; - phdr->p_offset = kc_vaddr_to_offset(m->addr) + dataoff; - phdr->p_vaddr = (size_t)m->addr; - if (m->type == KCORE_RAM) - phdr->p_paddr = __pa(m->addr); - else if (m->type == KCORE_TEXT) - phdr->p_paddr = __pa_symbol(m->addr); - else - phdr->p_paddr = (elf_addr_t)-1; - phdr->p_filesz = phdr->p_memsz = m->size; - phdr->p_align = PAGE_SIZE; - } - - /* - * Set up the notes in similar form to SVR4 core dumps made - * with info from their /proc. - */ - nhdr->p_offset = offset; - - /* set up the process status */ - notes[0].name = CORE_STR; - notes[0].type = NT_PRSTATUS; - notes[0].datasz = sizeof(struct elf_prstatus); - notes[0].data = &prstatus; - - memset(&prstatus, 0, sizeof(struct elf_prstatus)); + down_read(&kclist_lock); - nhdr->p_filesz = notesize(¬es[0]); - bufp = storenote(¬es[0], bufp); + get_kcore_size(&nphdr, &phdrs_len, ¬es_len, &data_offset); + phdrs_offset = sizeof(struct elfhdr); + notes_offset = phdrs_offset + phdrs_len; + + /* ELF file header. */ + if (buflen && *fpos < sizeof(struct elfhdr)) { + struct elfhdr ehdr = { + .e_ident = { + [EI_MAG0] = ELFMAG0, + [EI_MAG1] = ELFMAG1, + [EI_MAG2] = ELFMAG2, + [EI_MAG3] = ELFMAG3, + [EI_CLASS] = ELF_CLASS, + [EI_DATA] = ELF_DATA, + [EI_VERSION] = EV_CURRENT, + [EI_OSABI] = ELF_OSABI, + }, + .e_type = ET_CORE, + .e_machine = ELF_ARCH, + .e_version = EV_CURRENT, + .e_phoff = sizeof(struct elfhdr), + .e_flags = ELF_CORE_EFLAGS, + .e_ehsize = sizeof(struct elfhdr), + .e_phentsize = sizeof(struct elf_phdr), + .e_phnum = nphdr, + }; - /* set up the process info */ - notes[1].name = CORE_STR; - notes[1].type = NT_PRPSINFO; - notes[1].datasz = sizeof(struct elf_prpsinfo); - notes[1].data = &prpsinfo; + tsz = min_t(size_t, buflen, sizeof(struct elfhdr) - *fpos); + if (copy_to_user(buffer, (char *)&ehdr + *fpos, tsz)) { + ret = -EFAULT; + goto out; + } - memset(&prpsinfo, 0, sizeof(struct elf_prpsinfo)); - prpsinfo.pr_state = 0; - prpsinfo.pr_sname = 'R'; - prpsinfo.pr_zomb = 0; + buffer += tsz; + buflen -= tsz; + *fpos += tsz; + } - strcpy(prpsinfo.pr_fname, "vmlinux"); - strlcpy(prpsinfo.pr_psargs, saved_command_line, sizeof(prpsinfo.pr_psargs)); + /* ELF program headers. */ + if (buflen && *fpos < phdrs_offset + phdrs_len) { + struct elf_phdr *phdrs, *phdr; - nhdr->p_filesz += notesize(¬es[1]); - bufp = storenote(¬es[1], bufp); + phdrs = kzalloc(phdrs_len, GFP_KERNEL); + if (!phdrs) { + ret = -ENOMEM; + goto out; + } - /* set up the task structure */ - notes[2].name = CORE_STR; - notes[2].type = NT_TASKSTRUCT; - notes[2].datasz = arch_task_struct_size; - notes[2].data = current; + phdrs[0].p_type = PT_NOTE; + phdrs[0].p_offset = notes_offset; + phdrs[0].p_filesz = notes_len; - nhdr->p_filesz += notesize(¬es[2]); - bufp = storenote(¬es[2], bufp); + phdr = &phdrs[1]; + list_for_each_entry(m, &kclist_head, list) { + phdr->p_type = PT_LOAD; + phdr->p_flags = PF_R | PF_W | PF_X; + phdr->p_offset = kc_vaddr_to_offset(m->addr) + data_offset; + phdr->p_vaddr = (size_t)m->addr; + if (m->type == KCORE_RAM) + phdr->p_paddr = __pa(m->addr); + else if (m->type == KCORE_TEXT) + phdr->p_paddr = __pa_symbol(m->addr); + else + phdr->p_paddr = (elf_addr_t)-1; + phdr->p_filesz = phdr->p_memsz = m->size; + phdr->p_align = PAGE_SIZE; + phdr++; + } -} /* end elf_kcore_store_hdr() */ + tsz = min_t(size_t, buflen, phdrs_offset + phdrs_len - *fpos); + if (copy_to_user(buffer, (char *)phdrs + *fpos - phdrs_offset, + tsz)) { + kfree(phdrs); + ret = -EFAULT; + goto out; + } + kfree(phdrs); -/*****************************************************************************/ -/* - * read from the ELF header and then kernel memory - */ -static ssize_t -read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos) -{ - char *buf = file->private_data; - size_t size, tsz; - size_t elf_buflen; - int nphdr; - unsigned long start; - size_t orig_buflen = buflen; - int ret = 0; + buffer += tsz; + buflen -= tsz; + *fpos += tsz; + } - down_read(&kclist_lock); - size = get_kcore_size(&nphdr, &elf_buflen); + /* ELF note segment. */ + if (buflen && *fpos < notes_offset + notes_len) { + struct elf_prstatus prstatus = {}; + struct elf_prpsinfo prpsinfo = { + .pr_sname = 'R', + .pr_fname = "vmlinux", + }; + char *notes; + size_t i = 0; - if (buflen == 0 || *fpos >= size) - goto out; + strlcpy(prpsinfo.pr_psargs, saved_command_line, + sizeof(prpsinfo.pr_psargs)); - /* trim buflen to not go beyond EOF */ - if (buflen > size - *fpos) - buflen = size - *fpos; - - /* construct an ELF core header if we'll need some of it */ - if (*fpos < elf_buflen) { - char * elf_buf; - - tsz = elf_buflen - *fpos; - if (buflen < tsz) - tsz = buflen; - elf_buf = kzalloc(elf_buflen, GFP_KERNEL); - if (!elf_buf) { + notes = kzalloc(notes_len, GFP_KERNEL); + if (!notes) { ret = -ENOMEM; goto out; } - elf_kcore_store_hdr(elf_buf, nphdr, elf_buflen); - if (copy_to_user(buffer, elf_buf + *fpos, tsz)) { - kfree(elf_buf); + + append_kcore_note(notes, &i, CORE_STR, NT_PRSTATUS, &prstatus, + sizeof(prstatus)); + append_kcore_note(notes, &i, CORE_STR, NT_PRPSINFO, &prpsinfo, + sizeof(prpsinfo)); + append_kcore_note(notes, &i, CORE_STR, NT_TASKSTRUCT, current, + arch_task_struct_size); + + tsz = min_t(size_t, buflen, notes_offset + notes_len - *fpos); + if (copy_to_user(buffer, notes + *fpos - notes_offset, tsz)) { + kfree(notes); ret = -EFAULT; goto out; } - kfree(elf_buf); + kfree(notes); + + buffer += tsz; buflen -= tsz; *fpos += tsz; - buffer += tsz; - - /* leave now if filled buffer already */ - if (buflen == 0) - goto out; } /* * Check to see if our file offset matches with any of * the addresses in the elf_phdr on our list. */ - start = kc_offset_to_vaddr(*fpos - elf_buflen); + start = kc_offset_to_vaddr(*fpos - data_offset); if ((tsz = (PAGE_SIZE - (start & ~PAGE_MASK))) > buflen) tsz = buflen; - - while (buflen) { - struct kcore_list *m; + while (buflen) { list_for_each_entry(m, &kclist_head, list) { if (start >= m->addr && start < (m->addr+m->size)) break; @@ -557,7 +490,6 @@ out: return orig_buflen - buflen; } - static int open_kcore(struct inode *inode, struct file *filp) { if (!capable(CAP_SYS_RAWIO)) _
